Research And Design Of The New LED Street Lighting Driver Based On DSP Control

LED street lighting is a light source that has the advantage of high efficiency,energy saving, environmental protection, long life, etc. LED industry has developed rapidly in recent years, and gradually become the dominantion in lighting market. LED street lighting driver, as the power supply system for LED, whose performance is the key factor to guarantee the integral properties of the LED lighting system. So the high reliability, high power factor, long life and low cost of the LED street lighting driver must be guaranteed. The electrolytic capacitor is often used in traditional LED street lighting driver, while the life time of electrolytic capacitor is very short with only several thousand hours. Thus, the use of electrolytic capacitor is the main reason for restricting the long-term reliability of the LED street lighting and its driver.In this paper, a new LED street lighting driver based on DSP control is proposed according to the problem of short life time of LED street lighting driver, which is caused by utilization of electrolytic capacitor. The electrolytic capacitor is removed and the digitalization of the control segment is achieved in this design. And the theoretical analysis and design is conducted on the new LED street lighting driver. The driver is composed of three stage circuits and contains four independent outputs. The first stage is the boost PFC(power factor correction) converter to achieve high PF(power factor).As it does not use electrolytic capacitor to filter, the output voltage ripple is larger than using it, which directly affect the overall performance of the LED driver. Consequently,it needs to be optimized through the second and third stages. The second stage is the two-output LLC resonant converter based on open loop control which is driven by DSP.This stage provides galvanic isolation while reducing the voltage. The third stage is the four TIBuck(Two-Input Buck) converters based on DSP control that reduces the low-frequency ripple generated from the first two stages. Moreover, the current regulation of each LED street lighting driver is achieved and the constant current for four-channel LED street lighting is provided at this stage. The main works of this paper are:(1)This paper analyzes the life time of electrolytic capacitor and indicates the influence of electrolytic capacitor on circuit performance.(2)The power factor correction circuit and its control method are studied. Then thetheory analysis and parameter design of the power factor correction circuit is discussed.(3)This paper researches the working principle of the LLC resonant converter based on open loop control. Further, the design of the transformer and resonant tank parameters are accomplished.(4)The working principle and efficiency of the TIBUCK circuit are studied and analyzed, and its small-signal model which works in the continuous inductor current mode is presented. Then the main parameters are designed.(5)The new LED street lighting driver used TMS320F2812 as the control core to control the LLC resonant converter and TIBUCK constant current circuit. Next, the software flow chart of the main program and control subprogram are given.(6)The simulation model of the new LED street lighting driver with MATLAB/SIMULINK is established and the results are analyzed. Based on the theoretical analysis and simulation, a prototype of the new LED street lighting driver based on DSP control is built for experimental demonstration.The simulation and experimental results show that the new LED street lighting driver based on DSP control can achieve high power factor and good constant current characteristic without electrolytic capacitor. So this new LED driver can be used to driver high power LED street lighting.